1. Field of the Invention
The present invention relates generally to a bending apparatus for bending weatherstripping, core bars of weatherstrips, or the like.
2. Description of the Related Art
As is well known, a core bar, which is embedded in solid rubber for forming weatherstrips, is subjected to bending processing beforehand in accordance with a shape of a vehicle body opening portion to be covered by the weatherstrip. Conventionally, a stretch bending system, a draw bending system and a press bending system are well known.
However, according to the stretch bending system, terminal portions of the core bar, or weatherstrip must be clamped before effecting bending processing, the clamped ends being discarded after processing such that wastage of material and additional labour required become drawbacks of this process.
According to the draw bending method, it is possible to effect bending of weatherstripping into various shapes by replacing appropriately shaped wheels of varying sizes according to the shape desired. However, according to this method, only two-dimensional shapes are available, which may be insufficient for modern processing requirements.
According to the press system, as for example shown in FIG. 8, a straight piece of core bar 2 is set across an appropriately shaped mold groove 1a of a lower mold 1 while an upper mold 3 having a reciprocally shaped mold projection 3a is lowered into the core bar 2 to effect bending operation. However, according to such press system bending processing, springback may occur to the article (i. e. the core bar 2) after processing such that the article may parially resume its orignal shape. Thus, such occurence of springback must be taken into consideration in the shape of the mold and additional engineering complexity and increased costs are incurred.
Also, according to press type bending processing, when the upper and lower molds 3, 2 are brought together, the molding pressure therebetween as applied to the core bar 2 is uneven along the length of the core bar 2. Thus, particularly when a length of rubber weatherstripping is fitted over the core bar to be processed, such non-uniform molding pressure may cause folds and/or wrinkles in the finished article or mahy otherwise and may marr the finished appearance and/or performance of the finished article.
Therefore it has been required to provide a bending processing apparatus which can apply substantially uniform pressure during molding and which can effect a wide range of bending operations without need of mold replacement or substantial retooling.